1. Field of the Invention
The present invention relates to wireless signal reception technique, especially to wireless signal reception technique using maximum likelihood detection.
2. Description of Related Art
Nowadays wireless communication technique is widely spread and users have more and more demand for data throughput. Therefore, this industry field keeps studying how to increase bandwidth usage efficiency under limited system bandwidth and raise system throughput. A market trend is using a spatial multiplexing transmission manner of multiple-input multiple-output (MIMO) technique which can greatly raise system throughput without engaging more bandwidth. This transmission manner gets a lot of attention recently.
The spatial multiplexing transmission manner uses a plurality of antennas of a transmitter to transmit signals independent of one another through the same frequency band at the same time, while a receiver uses a plurality of antennas to receive and detect these signals. In order to achieve better demodulation efficiency, the receiver may use a maximum likelihood algorithm (ML algorithm). The ML algorithm could be understood as an algorithm in search of an optimum solution. The ML algorithm makes use of an exhaustive search manner to estimate an optimum solution of transmission signals among all possible solutions according to reception signals. However, the exhaustive search manner is not an efficient manner because it computes all of the possible solutions and takes a long time to measure processing latency, complexity and computation power.
People who are interested in the prior arts may refer to the following literatures:    (1) China patent application of publication number CN101582748A; and    (2) Massimiliano Siti, Michael P. Fitz, “A Novel Soft-Output Layered Orthogonal Lattice Detector for Multiple Antenna Communications”, IEEE International Conference on Communications (ICC), 2006.